There are no items to increase the trist with them as with the girls. They get trust solely through events where it sometimes depends on your choice if it increases or decreases.
As far as I can tell, his opinion on you mainly depends on how you treat slaves in all of Dorgania since he was himself enslaved in this horrible country that I sure hope will eventually be able to convince king Lancafew to abolish slavery and give equal rights to live freely to everyone.
I did not know in fact, I use Google Translation to write but message in English, as I am unable to write or read English, and my last message I believe I have sent in English
